The present invention relates to mixing and proportioning valves, such as for hot and cold water faucets, and more particularly to such valves of the type wherein the fluid flows through flexible valve tubes which are compressed or pinched by a valve member to vary the fluid flow.
This general type of valve is disclosed, for example, in my U.S. Pat. No. 4,359,067, which is a single control proportioning valve utilizing an elongated cam member which moves axially between the two tubes between extended, fully open and retracted fully closed positions for varying the total flow, and is also rotatable about its axis for selectively proportioning the flow between the two tubes. In that device, the tubes, in their as-fabricated or fully relaxed condition, are circularly cylindrical straight tubes. In use, the cam member always bears against the valve tubes, even in the fully-open position of the cam member, so that the valve tubes are at least partially compressed or pinched, resulting in a reduced flow area which has a flattened cross section, even in the fully-open position. This arrangement is necessary to limit the axial distance that the valve member must move between the fully open and fully closed conditions of the valve, otherwise the valve would be undesirably large.
In that prior type of flexible tube valve, when the valve tubes are pinched or compressed, the flattened ends project outwardly beyond the relaxed outer diameter of the valve tube, requiring a larger space in the valve body to accommodate the valve tubes in their pinched or closed conditions. This places a lower limit on the size of the valve assembly and militates against miniaturization thereof.
Another disadvantage of this prior type of flexible tube valve is that, while it is less noisy than other types of valves, there is still some noise. The camming surface of the cam member has a generally frustoconical portion and, as it moves from the fully open to the fully closed position it tends to close the upper portion of the valve tube before the lower portion, resulting in a generally teardrop-shaped opening. This results in some turbulence which can create a noise in the valve.
In prior dual control valves of the flexible tube type, each flexible tube is carried in a separate cartridge assembly which must be separately installed and removed. Furthermore, access to these cartridges in prior dual control valves has been fairly difficult, requiring disassembly of other parts of the valve with the use of tools.
Another problem with prior single-control valves of the flexible tube type is that the internal fluid pressure in the valve tubes counters the pinching action of the cam member when it is in the open position and tends to pop the cam member out to a fully open position. Since the desired normal rest condition for a faucet valve is in the fully closed condition, this necessitates a valve construction which tends to hold itself in the closed condition. The force required to effect this holding action must, of course, be overcome by the user in opening the valve, which militates against ease of valve operation.